1. Field of the Invention
This invention relates to the cutting of vegetation, and more particularly to the cutting of vegetation using a flexible, non-metallic cutting line extending from a rotating head and having means for automatically advancing an increment of line as it shortens.
2. Description of the Prior Art
A flexible line trimmer has a rotating head that is driven by an electrical or gasoline motor. The head includes a housing which has an aperture at its periphery. A spool is located in the housing containing a supply of coiled Nylon line. The line extends out the aperture into a cutting plane for trimming the vegetation.
Abrasion on the line during trimming causes the line to shorten fairly rapidly. Also, the line may break. In early versions of these devices, to advance additional line, the motor had to be stopped and the line physically pulled from the spool while disengaging some type of locking mechanism.
In subsequent versions, feeding an increment of line while operating became possible. Generally, these types had a line feeding mechanism in the head. When the operator bumped the head on the ground, drive teeth would disengage and re-engage to feed out an additional increment of line. While successful, it requires the operator to realize when the line is becoming short, which is not often easy. Also, some of the mechanisms tended to stick, and fail to properly feed out the line.
Recently, proposals have been made to automatically feed out an increment of line by using centrifugal force as the line shortens. The speed of the cutting head will automatically increase when the line shortens, thus increasing the centrifugal force. Devices using this principle are shown in U.S. Pat. No. 4,285,127, Zerrer, et al., Aug. 25, 1981, and U.S. Pat. No. 4,347,666, Moore, Sept. 7, 1982.